His name is François Voisin. He is 40 years old, and in the eyes of his wife and children, he's a modest, retiring man who works as a specialist in the repair of switchboards. However, in reality, François is one of the highest ranking French secret service agents. One day, he discovers clues that his wife may be intimately involved with a man by the name of Marcel. Offended and yet intrigued by the idea that his wife could cheat on him, François taps her phone turns his spying expertise on her...